Physical Characterization of Two Fractured Sedimentary Rock Aquifers in New Brunswick, Canada with Emphasis on the Development of Self-potential Methods PDF Download
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Author: Aaron DesRoches
Publisher:
ISBN:
Category : Aquifers
Languages : en
Pages : 279
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Book Description
Heterogeneity and anisotropy associated with fractured rock aquifers can make predicting fluid flow pathways difficult using traditional hydraulic testing methods alone. Surface-based self-potentials (SP) measured during pumping and hydraulic testing have been shown in this thesis to provide valuable information used to infer water table drawdown, preferential flow paths and hydraulic properties. To provide a basis for investigating the SP approach in fractured rock, conceptual models were first developed for two separate aquifers. Fracture patterns, combined with pump test and geophysical logging data allowed for flow directions to be assessed within a confined fluvial sandstone-shale aquifer underlying the Springdale wellfield in the Carboniferous Moncton Subbasin. In the Ordovician to Silurian Matapédia Basin, fracture characteristics were measured within the folded turbidite sequences underlying the Black Brook Watershed, and combined with hydraulic conductivity estimates derived from packer testing to provide a better understanding of heterogeneity responsible for anisotropic groundwater flow conditions. Both fractured aquifers were subsequently investigated through SP monitoring and numerical modelling. Transient SP signals recorded during pumping in the Springdale wellfield, combined with measurements of the electrokinetic voltage coupling coefficient, allowed spatial and temporal variations in drawdown to be inferred below electrodes positioned around the pumping well. SP-derived drawdown was fitted to the Theis model to obtain transmissivity and storativity estimates at electrode locations. Numerical modelling showed surface SP measurements to be an excellent proxy for hydraulic head at the top of an underlying confined aquifer even in the presence of hydraulic and electrical heterogeneities. SP signals recorded in the Black Brook watershed during a constant head injection test at a depth of 44 m were used to infer azimuthal anisotropy in fluid flow in directions consistent with dominant fracture set orientations. Numerical modelling showed that fracture transmissivity, length, and frequency all contribute to the magnitude and shape of SP anomalies recorded on surface resulting from flow from the highly transmissive fractures into the surrounding rock matrix. Results from the SP monitoring approach, combined with the conceptual aquifer models, demonstrated an inexpensive and non-invasive means of assessing water table drawdown pattern, preferential flow directions, and hydraulic properties estimates without the need for additional wells.
Author: Aaron DesRoches
Publisher:
ISBN:
Category : Aquifers
Languages : en
Pages : 279
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Book Description
Heterogeneity and anisotropy associated with fractured rock aquifers can make predicting fluid flow pathways difficult using traditional hydraulic testing methods alone. Surface-based self-potentials (SP) measured during pumping and hydraulic testing have been shown in this thesis to provide valuable information used to infer water table drawdown, preferential flow paths and hydraulic properties. To provide a basis for investigating the SP approach in fractured rock, conceptual models were first developed for two separate aquifers. Fracture patterns, combined with pump test and geophysical logging data allowed for flow directions to be assessed within a confined fluvial sandstone-shale aquifer underlying the Springdale wellfield in the Carboniferous Moncton Subbasin. In the Ordovician to Silurian Matapédia Basin, fracture characteristics were measured within the folded turbidite sequences underlying the Black Brook Watershed, and combined with hydraulic conductivity estimates derived from packer testing to provide a better understanding of heterogeneity responsible for anisotropic groundwater flow conditions. Both fractured aquifers were subsequently investigated through SP monitoring and numerical modelling. Transient SP signals recorded during pumping in the Springdale wellfield, combined with measurements of the electrokinetic voltage coupling coefficient, allowed spatial and temporal variations in drawdown to be inferred below electrodes positioned around the pumping well. SP-derived drawdown was fitted to the Theis model to obtain transmissivity and storativity estimates at electrode locations. Numerical modelling showed surface SP measurements to be an excellent proxy for hydraulic head at the top of an underlying confined aquifer even in the presence of hydraulic and electrical heterogeneities. SP signals recorded in the Black Brook watershed during a constant head injection test at a depth of 44 m were used to infer azimuthal anisotropy in fluid flow in directions consistent with dominant fracture set orientations. Numerical modelling showed that fracture transmissivity, length, and frequency all contribute to the magnitude and shape of SP anomalies recorded on surface resulting from flow from the highly transmissive fractures into the surrounding rock matrix. Results from the SP monitoring approach, combined with the conceptual aquifer models, demonstrated an inexpensive and non-invasive means of assessing water table drawdown pattern, preferential flow directions, and hydraulic properties estimates without the need for additional wells.
Author: Jeremy R. Patterson
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Fractured sedimentary bedrock aquifers represent critical groundwater resources that provide significant domestic and agricultural water supplies as well as idealized targets for wastewater storage and alternative energy development. The complex flow pathways occurring within fractured bedrock has led to flow and transport phenomena that are critical to understand, yet difficult to predict, highlighting the necessity of moving beyond traditional porous media approaches to modeling bedrock fracture flow and transport. Characterizing the physical properties that govern fluid flow and storage in bedrock fractures represents a critical first step in developing the next generation of models that capture these complex hydraulic processes. Recent field and modeling studies highlight oscillatory flow interference testing as a novel pressure-based approach to characterize the hydraulic properties of bedrock fractures, and found that the returned effective hydraulic parameters show an apparent period-dependence when using simplified modeling approaches. In this dissertation, I use a combination of field and numerical modeling experiments to investigate a range of potential mechanisms - such as heterogeneity, fracture-host rock fluid exchange, and fracture hydromechanics - that might be contributing to this apparent period-dependence. Chapter 2 describes a novel gradient-based inversion strategy to determine effective aquifer flow properties and provides uncertainty estimates in returned parameters. This analysis shows that a multi-frequency inversion approach provides additional information that helps constrain the inversion and reduces parameter uncertainty estimates. Chapter 3 describes 209 oscillatory flow experiments conducted at a fractured sedimentary bedrock site near Madison, Wisconsin. Using simplified analytical modeling approaches, this analysis shows an apparent period-dependence in the collected field data, and indicates non-Darcian flow, borehole storage, and fracture leakance do not contribute to the apparent period dependence at our field site. Chapter 4 presents a comprehensive numerical modeling study that systematically explores fracture aperture heterogeneity, fracture-host rock fluid exchange, and fracture hydromechanical behavior to explain the apparent period-dependence. This analysis shows that fracture hydromechanical behavior is the only investigated mechanism that consistently reproduces the previously reported period-dependent parameter trends in direction and magnitudes of change, though other explored mechanisms produce period-dependent trends that could represent helpful diagnostic criteria of processes occurring at a specific site. Overall, the results of this dissertation highlight the need to develop more complex numerical modeling approaches that account for complex fracture hydraulics when characterizing fractured bedrock aquifer systems.
Author: Richard Ayuk II. Akoachere
Publisher:
ISBN:
Category : Aquifers
Languages : en
Pages : 328
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Pablo A. Cello
Publisher:
ISBN: 9781243751928
Category :
Languages : en
Pages : 232
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Book Description
Important aquifers, petroleum reservoirs, geothermal reservoirs, and waste disposal sites throughout the world are located in fractured rock formations. Responsible management of these resources and sites requires appropriate field characterization studies and modeling techniques to assess the impact of management alternatives. Characterization and modeling of aquifers is particularly challenging in fractured media, where flow is concentrated into channels and thus violates the assumptions of traditional analysis approaches. The General Radial Flow (GRF) model is an alternative method for hydraulic test interpretation that infers an additional parameter, the flow dimension n, to describe the flow geometry. Previous studies have reported non-integer flow dimensions for a number of aquifers and reservoirs of various rock types, suggesting that flow is dominated by a series of fractal channels [Acuna and Yortsos, 1995]. Typically, the information carried by the flow dimension is ignored in subsequent modeling studies. The present work is a Monte Carlo analysis of numerical models of aquifer tests in two-dimensional fractured media, with the objective to identify stochastic models of aquifer heterogeneity that consistently produce stable apparent flow dimensions in agreement with those inferred from aquifer test conducted in fractured rock aquifers. The flow dimension is examined first for three conventional stochastic models of the transmissivity field: multivariate log Gaussian (mvG), Fractional Brownian Motion (fBm), and Site Percolation Network (SPN). Then, the more realistic discrete fracture network (DFN) model, with fracture lengths distributed as a power-law is analyzed. The study is focused on the relationships among the parameters of a DFN, the flow dimension, and the regime of diffusion of pressure transients of aquifer tests (e.g., Fickian or non-Fickian). Results demonstrate that the DFN model is the best candidate to represent the heterogeneity of fractured rock aquifers. In particular for the DFN model, the apparent flow dimension and anomalous diffusion exponent k depend on both the density and the power of the fracture length distribution, and thus also on the connectivity regime of the fracture network system. Depending on the connectivity regime, the apparent flow dimension stabilizes to less than the Euclidean dimension and the apparent value of k
Author: Patrick Quinn
Publisher:
ISBN:
Category :
Languages : en
Pages : 184
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Book Description
Packer tests in boreholes in fractured rock involving injection or withdrawal of water in borehole segments have been standard practice in bedrock hydraulic investigations pertaining to geotechnical and water resource projects since the 1950's. However in contaminant hydrogeology, the tests are conducted to assess groundwater velocity and contaminant fluxes and therefore, much improved resolution and measurement accuracy is needed. For this thesis study packer testing equipment was designed specifically for studies of contaminant behavior in fractured rock with the ability to conduct four types of hydraulic tests: constant head/flow injection step tests, slug tests, pumping tests and recovery tests, all in the same borehole test interval without removing the equipment from the hole while acquiring high precision data for calculation of transmissivity (T) and fracture hydraulic apertures (2b). This equipment records pressure above, within, and below the test interval to gain insights regarding open borehole flow patterns, and to identify short circuiting to the open borehole above or below the test interval. The equipment measures flow rates as low as 6 ml/min up to 20 L/min, and the temperature in the test interval and at the ground surface is measured to account for density and viscosity variations. Each type of test is conducted repeatedly over a wide range of imposed applied pressures and flow rates and the equipment was applied to assess performance of this new methodology for packer testing and gain new insights concerning fractured rock hydrology in 6 boreholes in the fractured dolostone aquifer underlying the City of Guelph, Ontario. In the first stage of the equipment application in the fractured dolostone aquifer, over 150 high precision straddle packer tests using constant rate injection (Q) were conducted to identify the conditions of change from Darcian (linear) to non-Darcian (non-linear) flow based on the Q vs dP relationship where dP is the applied pressure above ambient. In the Darcian regime, the linear Q vs dP relationship passes through the origin (0,0) where the ambient pressure represents static conditions (i.e. Q=0 and dP=0). After the onset of non-Darcian flow, proportionally less Q per unit dP occurs so that the interval transmissivity (T) calculated from the test results using Darcy's Law based models is underestimated by as much as an order of magnitude. The Darcy-Missbach equation was found to be a robust conceptual model for representation of step constant Q tests in which the linear proportionality constant relates Qn vs dP. It was found that quantifying non-linear flow allows for a more accurate determination of the linear data to obtain better estimates of T and hence the hydraulic apertures derived from the T using the Cubic Law. In order to obtain hydraulic apertures from the packer test T values, the number of hydraulically active fractures in the test interval is needed. The only data collected regarding individual fractures was the core log created during the coring process and the acoustic televiewer log, both of which identify the location of fractures, but neither could tell if the fractures identified were hydraulically active. A sensitivity analysis concerning the effects of non-linear flow and the number of hydraulically active fractures on the calculated hydraulic aperture shows that the number of fractures selected as hydraulically active has the greatest effect on the aperture values. A new approach is proposed for determining apertures from hydraulic tests in fractured rock utilizing the onset of non-linear flow to aid in the choice of the number of active fractures present in the test interval. In the second stage of the equipment application, the four types of hydraulic tests (constant head, pumping, recovery, and rising/falling head slug tests) conducted in the same test interval at gradually increasing flow rates showed that non-linear flow can be most easily identified and quantified using constant head tests providing a higher degree of certainty that the data used to calculate T are from the Darcian flow regime. Slug tests are conducted most rapidly, but formation non-linear behavior is commonly exaggerated by non-linearity within the test equipment at large initial displacements. However, the equipment non-linearity can be accounted for using a Reynolds number (Re) analysis allowing identification of the non-linear flow in the formation. In addition, non-linear flow can interfere with evidence of fracture dilation. The pumping and recovery tests are the most time consuming because of the relatively long time required to reach steady state. However, these tests offer the most potential to give insight into the influences of the peripheral fracture network and rock matrix permeability on test results In addition to the actual transmissivity of the test interval T values obtained from packer tests can be influenced by several factors including non-linear flow in the formation and in the test equipment, aperture dilation or closure, hydraulic short circuiting or leakage from the test interval to the open borehole and dual permeability properties of the system (fractures and matrix). The equipment and procedures developed in this thesis provide an improved framework for identifying these influences and in some cases avoiding them so that the aperture values calculated from T measurements are more accurate than those obtained through conventional approaches. In the conventional procedures for packer testing in fractured rock as recommended in manuals and guidance documents, the applied head and flow rate can be expected, based on the results of this thesis, to produce transmissivity values biased low because of non-linear (non-Darcian) flow.
Author: Deborah V Chapman
Publisher: CRC Press
ISBN: 0419215905
Category : Science
Languages : en
Pages : 658
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Book Description
This guidebook, now thoroughly updated and revised in its second edition, gives comprehensive advice on the designing and setting up of monitoring programmes for the purpose of providing valid data for water quality assessments in all types of freshwater bodies. It is clearly and concisely written in order to provide the essential information for all agencies and individuals responsible for the water quality.
Author:
Publisher:
ISBN:
Category : Groundwater
Languages : en
Pages : 220
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Author: Steven Earle
Publisher:
ISBN: 9781537068824
Category :
Languages : en
Pages : 628
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Book Description
This is a discount Black and white version. Some images may be unclear, please see BCCampus website for the digital version.This book was born out of a 2014 meeting of earth science educators representing most of the universities and colleges in British Columbia, and nurtured by a widely shared frustration that many students are not thriving in courses because textbooks have become too expensive for them to buy. But the real inspiration comes from a fascination for the spectacular geology of western Canada and the many decades that the author spent exploring this region along with colleagues, students, family, and friends. My goal has been to provide an accessible and comprehensive guide to the important topics of geology, richly illustrated with examples from western Canada. Although this text is intended to complement a typical first-year course in physical geology, its contents could be applied to numerous other related courses.
Author: National Research Council
Publisher: National Academies Press
ISBN: 0309125391
Category : Nature
Languages : en
Pages : 611
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Book Description
The rapid conversion of land to urban and suburban areas has profoundly altered how water flows during and following storm events, putting higher volumes of water and more pollutants into the nation's rivers, lakes, and estuaries. These changes have degraded water quality and habitat in virtually every urban stream system. The Clean Water Act regulatory framework for addressing sewage and industrial wastes is not well suited to the more difficult problem of stormwater discharges. This book calls for an entirely new permitting structure that would put authority and accountability for stormwater discharges at the municipal level. A number of additional actions, such as conserving natural areas, reducing hard surface cover (e.g., roads and parking lots), and retrofitting urban areas with features that hold and treat stormwater, are recommended.
